U.S. Pat. No. 5,108,296, discloses a technique for body grounding by opening a hole in the painted surface of a conductive attaching body, such as an automobile body, and fastening together a lead wire and bus bar with screws.
In this example of the prior art, a conductive member having a bent piece is inserted into a hole formed adjacent to an attachment hole of an insulated mounting block. The surface of the mounting block on which a conductive member is arranged makes planar contact with a conductive support structure so that the mounting block may be tightly fastened to a hole of the conductive support structure with a conductive screw inserted through the attachment hole. The end of the bent piece of the conductive member is connected to the inner surface of the hole of the conductive support structure with the conductive screw while making "scratching" contact with the inner surface of the screw head.
In attaching an interior lamp and the like by fastening with screws to the automobile body, since there are no reinforcing members (particularly on the inner surface and periphery of the cylindrical attachment hole of a plastic attached body), a problem is encountered wherein a completely satisfactory attachment state cannot always be obtained due to the cracking, cutting, tearing or breaking off of the mounting block by virtue of the powerful twisting force of the set screws.
In addition, there is also a problem of the conductive member, integrated into a single unit with a bus bar, becoming displaced by the turning force of the screws.
Furthermore, since the mounting block is attached by only its surface on which a conductive member is arranged, there has also been the problem of it being subjected to restrictions on its direction of attachment.
That is, since handling of lead wires and bus bars is troublesome at visible locations such as door switches and interior electrical components such as interior lamps (not to mention locations hidden from sight), the screws sometimes become loose due to vibrations and the like. As a result, numerous problems arose which required the use of spring washers.
Consequently, although there are other prior art examples which prevent partial damage to the mounting block by the screws, for example, by embedding a reinforcing ring by insertion-molding in line with the attachment hole, there is still the problem of molding costs becoming expensive due to the need for plastic insert molding means.
Therefore, although it is possible to consider simply tightly fitting a reinforcing ring in the cylindrical attachment hole, a press machine is required which also results in poor workability. In contrast, the case where the reinforcing ring is loosely fit, there are problems such as the ring easily falling out or still requiring the use of a spring washer.